I have a 20 year old diesel tank that has a small leak at or near a
bottom weld.

I've been thinking of taking it to a heliarc welder to attempt a
repair.

Comments?

Marc
I don't want to be a messenger of bad news, but I'm going to bet that the
tank should be replaced. I think it is very likely that the bottom of the
tank is severely coroded. This would be normal if the tank was not coated
inside.
Steve

"Marc Auslander" wrote in message
...
I have a 20 year old diesel tank that has a small leak at or near a
bottom weld.

I've been thinking of taking it to a heliarc welder to attempt a
repair.

Comments?

Welding is an option....

Another option is to use a tank lining epoxy, using glass cloth over
the weld seams, etc. to strengthen them. Just figure a way to cut
open the tank top and later apply a sister flange for re-closing,
etc.

I use: www.epoxyproducts.com for both potable water tanks and fuel
tank lining. Interlux Commercial Marine Division also offers tank
lining epoxies.

Rich is correct, but there is a huge risk that the epoxy will NOT bond to a
tank once it has carried fuel. Please ask the manufacturer if they recommend
their product to be used in the way you desire. I have just been through
this exercise.
Steve


"RichH" wrote in message
...
Welding is an option....

Another option is to use a tank lining epoxy, using glass cloth over
the weld seams, etc. to strengthen them. Just figure a way to cut
open the tank top and later apply a sister flange for re-closing,
etc.

I use: www.epoxyproducts.com for both potable water tanks and fuel
tank lining. Interlux Commercial Marine Division also offers tank
lining epoxies.

On 29 Mar 2008 10:10:43 -0400, Marc Auslander
wrote:

I have a 20 year old diesel tank that has a small leak at or near a
bottom weld.

I've been thinking of taking it to a heliarc welder to attempt a
repair.

Comments?

I imagine a water puddle helped the pinpoint corrosion. There may be
others waiting to break through too. I don't see why a welder couldn't
make a weak spot good. Notsure how he'd find any others, unless you
could look along the bottom inside, somehow.

Brian Whatcott Altus OK

On 29 Mar 2008 10:10:43 -0400, Marc Auslander
wrote:

I have a 20 year old diesel tank that has a small leak at or near a
bottom weld.

I've been thinking of taking it to a heliarc welder to attempt a
repair.

Comments?

Others have commented on the possibility that extensive corrosion may
exist. I'd like to comment on the heliarc.

If you can find a welder stupid enough to attempt to weld on your fuel
tank I strongly suggest that you do not stand around to watch.
There is a good possibility that the thing will explode unless fairly
extensive cleaning methods are used.

As I remember it, the USAF's procedure was to drain and wash the tank,
inside and out, using a strong soap solution; then steam clean the
inside of the tank for 30 minutes; then make the weld while the tank
was still hot from the steaming. If the tank cooled off during the
repair it had to be re-steamed.


Bruce-in-Bangkok
(correct email address for reply)

Bruce is somewhat correct ... the tank has to be padded with an inert
gas such as Nitrogen, etc. Welders on transmission lines 'hot-tap'
repairs all the time ... just need someone who KNOWS how to weld
such.

On Sat, 29 Mar 2008 21:59:03 -0700 (PDT), RichH
wrote:

Bruce is somewhat correct ... the tank has to be padded with an inert
gas such as Nitrogen, etc. Welders on transmission lines 'hot-tap'
repairs all the time ... just need someone who KNOWS how to weld
such.


The point about making a hot tap is that you are welding on a closed
pipe that is filled completely with oil - no air. some what different
then an empty tank.

I have no idea why the A.F. procedure was to steam the tank. Certainly
we had all kinds of inert gas available but that was the procedure.
Maybe because it worked?




Bruce-in-Bangkok
(correct email address for reply)

WaIIy wrote:


In high school shop class, I had a lawnmower gas tank I wanted to
solder.

I washed the tank with host soapy water and let water run through it for
about ten minutes. I then waited for it to dry.

As soon as I hit it with the torch, kaboom and there went part of my
left eyebrow.


I thought when welding fuel tanks you leave them full of water when you
do the welding.

22 years ago when we bought our sailboat, the surveyer missed the
slight diesel ooze/leaks from the main 180 gal diesel Al tank. We
found it after getting beat up on a reach - washed all the crud out of
the dozens ? of crevice corrosion tiny holes that were caused by a
number of s/s fasteners being left in the tank. The solution was to
cut access panels in the beautiful teak soles (ouch), cut the 3
largest size access ports possible in the tank top (it has 2 baffles)
and clean out the tank with paper towels, cloth and acetone and a big
fan. Then take a rotary s/s brush on a hand drill and completely
burnish to shiny clean scraped Al all the floor and walls up to 5-6"
above the floor - vacuum - and epoxy with West epoxy (no cloth) with
the slower hardener to hope to try to get some to "soak" into the
crevices. It's been 22 years and 2 circumnavigations - leaks not a
drop. Diesel has no effect on West epoxy. We've had the tanks open to
clean 3 times since and the epoxy looks like new.





On 29 Mar 2008 10:10:43 -0400, Marc Auslander
wrote:

I have a 20 year old diesel tank that has a small leak at or near a
bottom weld.

I've been thinking of taking it to a heliarc welder to attempt a
repair.

Comments?

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